Thermal aging and pyrolysis behavior of hyperbranched polymers grafted carbon fibers reinforced phthalonitrile/cyanate ester blend composites

This study investigates the long-term thermal-oxidative stability and mechanical properties of phenol-containing phthalonitrile monomer (PN75) and dicyanate ester of bisphenol-A (DCBA) composites reinforced with short carbon fibers T700SC (SCF) within a temperature range of 330−375 °C. The research focuses on the PN75 monomer and DCBA blend reinforced SCF composites with varying SCF content, examining mass loss and changes in flexural strength after thermal aging for 50 h (h). Results show that the SCF-reinforced composites based on the PN75/DCBA blend consistently outperform the neat blend in flexural strength, both at room temperature and after thermal aging. The introduction of the SCF significantly improves the composites' thermal stability and mechanical retention, with higher SCF content correlating to better performance. Notably, after aging at 350 °C, the SCF-reinforced composites based (30% (mass) SCF) retained 88.8% of its flexural strength, compared to 61.1% for the neat blend. Morphological analysis reveals that while thermal aging causes degradation of the PN75/DCBA blend layer on SCF surfaces, the overall composite structure maintains good mechanical properties up to 350 °C. At 375 °C, significant degradation occurs, yet the composites still retain flexural strengths above 78 MPa. This study demonstrates the potential of the SCF-reinforced composites based on PN75/DCBA blend for high-temperature applications, establishing their upper-temperature limit for long-term use in oxidative environments.